This invention is related to high solids coating compositions, in particular, to high solids acrylic coating compositions.
Conventional coating compositions of a high molecular weight acrylic polymer and melamine crosslinking resins are well known in the art as shown by Vasta U.S. Pat. No. 3,622,651, issued Nov. 23, 1971; Hick U.S. Pat. No. 3,841,895, issued Oct. 15, 1974; Parker U.S. Pat. No. 3,674,734, issued July 4, 1972 and Parker U.S. Pat. No. 3,637,546, issued Jan. 25, 1972. These patents illustrate high quality coating compositions. However, these compositions have a relatively high solvent content to provide for good application properties and good properties of the resulting dried finish. To utilize these compositions in areas which have strict air pollution regulations, pollution abatement equipment is required. This equipment is expensive and increases capital investment of a plant and is costly to operate. Any attempt to reduce the solvent content of these conventional compositions generally results in finishes which have either a poor appearance or unacceptable properties or both.
In an effort to obtain high solids coating compositions that can be applied by conventional spraying techniques, the molecular weight of the acrylic polymer used in these compositions was reduced substantially and solvent content of the coating compositions was reduced. The reduction in molecular weight caused a problem of poor appearance, particularly two tone metallic glamour, of finishes of these compositions when aluminum flake pigments were used therein. The poor appearance is caused by improper orientation of the aluminum flake in the finish.
There is a great need for a coating composition that has a low solvent content and that will meet current air pollution regulations but still provides a high quality finish with good two tone metallic glamour that is useful as an exterior finish for automobiles, trucks and airplanes. The high solids coating composition of this invention has these desirable characteristics.